Children's Hospital Colorado

Transposition of the Great Arteries

What is transposition of the great arteries?

Transposition of the great arteries (TGA) is a congenital heart defect that occurs when a baby's heart develops incorrectly in the womb. This condition is marked by the reversal of the heart's two most important blood vessels, the aorta and the pulmonary artery.

In a healthy heart, the aorta pumps oxygen-rich blood to the body and the pulmonary artery sends blood to the lungs. This is where the blood absorbs oxygen so that the oxygen-rich blood can then be pumped to the body. With transposition of the great arteries, however, not enough oxygen-rich blood circulates from the lungs to the body.

The most common form of TGA

Most infants with transposition of the great arteries are diagnosed with "D-type" or dextro-transposition. In this congenital abnormality, no oxygen-rich blood goes to the body and:

  • The aorta and pulmonary artery are switched, but the ventricles developed in the correct place.
  • Blood that returns to the heart from the body travels from the right atrium to the right ventricle, where it is pumped out to the body again, without ever going to the lungs.
  • Blood from the lungs comes back to the left atrium and then to the left ventricle, where it is pumped back out to the lungs through the pulmonary artery.

Who is at risk of transposition of the great arteries?

TGA is a very rare congenital heart defect. Boys are more susceptible to D-type transposition, although the reason is not known. Children with a family history of transposition are also more likely to develop the condition.

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